kV Energy Research Articles

Comparing the biological effectiveness of low energy 100 kV and high energy 5 MeV X-rays against Oriental fruit fly (Diptera: Tephritidae).

Radioisotope irradiators (using cesium-137 or cobalt-60) are used as sources of ionizing radiation to control quarantine or phytosanitary insect pests in internationally traded fresh commodities and to sterilize insects used in sterile insect release programs. There are institutional initiatives to replace isotopic irradiators (producing γ-rays) with lower-energy X-ray machines due to concerns about radiological terrorism and increasingly stringent regulations on the movement of radioisotopes. Questions remain about whether the biological effects of low-energy X-rays are comparable to those of γ-rays since differences in energy levels and dose rates of X-rays may have different efficacies. We compared adult emergence, flight ability, and adult survival in the Oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritdae), after irradiation of third instar larvae with 100 kV or 5 MeV (5,000 kV) X-rays at 20 and 40 Gy in replicated studies. At 20 Gy, the adult emergence rate was significantly lower after irradiation with 100 kV compared to 5 MeV X-rays, suggesting higher efficacy at the lower energy level. In a follow-up study using 100 kV X-rays, applying 20 Gy using a slow dose rate (0.24 Gy min-1) resulted in significantly higher adult emergence than did a fast dose rate (3.3 Gy min-1), suggesting lower efficacy. Although our study suggests higher efficacy of low energy 100 kV X-rays, there is uncertainty in measuring the dose from an X-ray tube operating at 100 kV using an ionization chamber; we discuss how this uncertainty may change the interpretation of the results. Using a 100 kV X-ray irradiator to develop a phytosanitary treatment may underestimate the dose required for insect control using commercial high-energy γ-ray or X-ray systems.

Radiation attenuation and elemental composition of locally available ceramic tiles as potential radiation shielding materials for diagnostic X-ray rooms

Ceramic materials are being explored as alternatives to toxic lead sheets for radiation shielding due to their favorable properties like durability, thermal stability, and aesthetic appeal. However, crafting effective ceramics for radiation shielding entails complex processes, raising production costs. To investigate local viability, this study evaluated Malaysian ceramic tiles for shielding in diagnostic X-ray rooms. Different ceramics in terms of density and thickness were selected from local manufacturers. Energy Dispersive X-ray Fluorescence (EDXRF) and X-ray Fluorescence (XRF) characterized ceramic compositions, while Monte Carlo Particle and Heavy Ion Transport code System (MC PHITS) simulations determined Linear Attenuation Coefficient (LAC), Half-value Layer (HVL), Mass Attenuation Coefficient (MAC), and Mean Free Path (MFP) within the 40–150 kV energy range. Comparative analysis between MC PHITS simulations and real setups was conducted. The C3–S9 ceramic sample, known for homogeneous full-color structure, showcased superior shielding attributes, attributed to its high density and iron content. Notably, energy levels considerably impacted radiation penetration. Overall, C3–S9 demonstrated strong shielding performance, underlining Malaysia's potential ceramic tile resources for X-ray room radiation shielding.

Clinical Characterization of a Novel Robotic IORT Unit

A novel mobile robotically-guided low-energy intra-operative radiation therapy device was characterized for clinical use. The compact system offers flexible positioning with treatment delivery up to 70 kV energy and 10 Gy/min dose rate with radially collimated emission, and underwent characterization for its dosimetric performance, positioning accuracy and overall clinical suitability. The Morpheus system (Empyrean Medical Systems) consists of a miniature electron esource and a partitioned partial-transmission tungsten target capable of producing 50, 60, and 70 kVp x-rays, mounted on a robotic arm and supported by a motorized mobile base. The radially collimated beam is partitioned in six segments with three radial positions per segment for selective emission, target irradiation and tissue sparing. The beam characteristics were assessed with ion chamber and film dosimetry, both in-air and in a water tank. Radiation levels were assessed for safety and shielding requirements. The absolute dose rate at the surface of a 2 cm radius sterilizable treatment balloon is 8 Gy/min for the 70 kV beam using the AAPM TG-61 formalism. The six treatments sectors emit radially in 60 degrees wedges to within +/- 15% of each other, which can be simply corrected for treatment delivery. The dose falls off to 50% of its initial value within 8 mm from the surface of a treatment balloon for a 70 kV beam. The robotic arm enables a free-hand positioning of the X-ray treatment head to within 1 mm. All interlocks and sterility requirements for operation within an operating room environment were found to be satisfactory. Radiation levels require mobile shielding or a shielded room to be within permissible public radiation levels. The clinical characterization shows the new unit provides a stable and flexible beam delivery platform suitable for IORT treatments. The simplified docking and collimated beam emission provides enhanced capabilities for patient treatment.

An experimental study on droplet-scale combustion and atomization behavior in pure ethanol, methanol, and trimethyl borate, and their blends

The combustion and atomization behavior of pure ethanol (EtOH), methanol (MeOH) and trimethyl borate (TMB) fuels and their blends prepared at 20 wt%, 40 wt%, 60 wt% and 80 wt% ratios were determined by processing videographs recorded with a high-speed camera and temperature data recorded with a thermal camera during droplet-scale combustion experiments performed at atmospheric pressure. EtOH and MeOH are good alternatives for transport due to their high oxygen content and relatively short carbon chains. TMB, an organoboron derivative in the liquid phase, is unique to creating a low-carbon emission and high-energy alternative fuel blend with boron, oxygen, and short carbon chains. This study focuses on the preparation of EtOH, MeOH, and TMB fuels and homogenized fuel mixtures with high energy values and the characterization of their combustion behavior. The experiments were carried out by suspending ethanol-trimethy borate (EtOH-TMB) and methanol-trimethyl borate (MeOH-TMB) fuel droplets on SiC wire and igniting them with an electrode producing an arc of 1 ms duration at 20 ms intervals with 6 kV energy. The results showed that EtOH and TMB formed a homogenized fuel mixture at all mixing ratios and the largest and most homogeneous green luminescence flame envelopes (depending on boron oxidation) were formed, indicating BO2 formation in almost all fuel mixtures. On the other hand, the droplets of MeOH-TMB fuel mixtures containing 20 wt%, 40 wt%, and 60 wt% MeOH exhibited the most favorable trend to the D2-law of diameter reduction during combustion. EtOH-TMB fuel droplets containing 60 wt% TMB exhibited the highest maximum flame temperature of 631 K. In this study, it has been shown that new-generation hybrid transportation fuels with no phase separation, low ignition delay times despite increased oxygen content, and high calorific value can be produced with hybrid fuel blends to be formed with TMB and alcohols. The results obtained will shed light on the literature for the solution to the problematic combustion characteristics of boron, which is tried to be used in many areas of the transportation industry.

PO-1762 Dosimetric properties of a water-based liquid scintillator for use in kV energy photon beams

PO-1762 Dosimetric properties of a water-based liquid scintillator for use in kV energy photon beams

Assessment of dentin mineral density of human teeth using micro-computed tomography in two kilovoltage levels

A significant advancement in micro-computed tomography (μCT) translational application in endodontics has occurred. The purpose of the study was to assess the applications of a new method to measure dentin mineral density (DMD) and to compare between 2 levels of energy sources. Two sets of standardized porous solid hydroxyapatite (HA) phantoms, with mineral densities of 0.25 g/cm3 and 0.75 g/cm3, respectively were embedded in aluminum foil. The μCT homogeneity and noise in the HA phantoms were analyzed using 50 kV and 100 kV energy sources. DMD of 66 extracted human teeth was measured at the cemento-enamel junction (CEJ), mid-root, and apical levels. Assessment included linearity between the energy source and the DMD measurement. The quality of the images obtained from the 2 energy sources was compared and analyzed statistically. HA phantom rods and validation methods showed that 100 kV provided a more accurate measurement of the DMD in all groups tested. The 100 kV 3D reconstructed µCT images displayed a more defined details of the dentin structure. A statistically significant difference was found between 100 and 50 kV (p < 0.05) in all measured areas except for the mid-root. Using micro-computed tomography is a practical and non-destructive method to measure dentin density. 100 kV energy source provides clearer and more consistent images.

Performance of a Novel Rear-Triggered 4H-SiC Photoconductive Semiconductor Switch

Radial lateral structure photoconductive switches are fabricated in this work via vanadium-doped 4H-SiC and high-purity 4H-SiC materials. The switches are triggered by 355- and 532-nm laser, and the performance of the switch is compared in the applied voltage range of 1–10 kV and laser energy range of 0.3–14 mJ. The experimental results show that the conduction current of the laser incident from the rear is larger. Simulations of the current density distribution of a 2-D cross section of the photoconductive switch provide theoretical support for this phenomenon. Additionally, the conduction current of the high-purity material is found to be higher than that of the vanadium-doped material under the same conditions.

The Initial Test of a Micro-Joules Trigger, Picosecond Response, Vertical GaN PCSS

To meet the miniaturization of all-solid-state high-power microwave drive technology based on photoconductive semiconductor switches (PCSSs), a vertical gallium nitride (GaN) PCSS that is triggered by a micro-joules energy and picoseconds pulse width laser is presented. The device has showed low triggering optical energy and fast response. When the bias-voltage is 3 kV and optical energy is 33 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{J}$ </tex-math></inline-formula> , the photocurrent, on-state resistance, rise-fall time and quantum efficiency of the PCSS are 4.28 A, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$650.5~\Omega $ </tex-math></inline-formula> , 412/370 ps and 0.28%, respectively. It is anticipated that GaN-based PCSS will have a practical application in future radio frequency (RF) microwave systems for military purposes.

Review of Shielding Evaluation Methodology for Facilities Using kV Energy Radiation Generating Devices Based on the NCRP-49 Report

Review of Shielding Evaluation Methodology for Facilities Using kV Energy Radiation Generating Devices Based on the NCRP-49 Report

Effects of Fully Filling Deep Electron/Hole Traps in Optically Stimulated Luminescence Dosimeters in the Kilovoltage Energy Range

Background: This study investigated the characteristics of optically stimulated luminescence dosimeters (OSLDs) with fully filled deep electron/hole traps in the kV energy ranges.Materials and Methods: The experimental group consisted of InLight nanoDots, whose deep electron/hole traps were fully filled with 5 kGy pre-irradiation (OSLD&lt;sub&gt;exp&lt;/sub&gt;), whereas the non-preirradiated OSLDs were arranged as a control group (OSLD&lt;sub&gt;cont&lt;/sub&gt;). Absorbed doses for 75, 80, 85, 90, 95, 100, and 105 kVp with 200 mA and 40 ms were measured and defined as the unit doses for each energy value. A bleaching device equipped with a 520-nm long-pass filter was used, and the strong beam mode was used to read out signal counts. The characteristics were investigated in terms of fading, dose sensitivities according to the accumulated doses, and dose linearity.Results and Discussion: In OSLD&lt;sub&gt;exp&lt;/sub&gt;, the average normalized counts (sensitivities) were 12.7%, 14.0%, 15.0%, 10.2%, 18.0%, 17.9%, and 17.3% higher compared with those in OSLD&lt;sub&gt;cont&lt;/sub&gt; for 75, 80, 90, 95, 100, and 105 kVp, respectively. The dose accumulation and bleaching time did not significantly alter the sensitivity, regardless of the filling of deep traps for all radiation qualities. Both OSLD&lt;sub&gt;exp&lt;/sub&gt; and OSLD&lt;sub&gt;cont&lt;/sub&gt; exhibited good linearity, by showing coefficients determination (R2) &gt; 0.99. The OSL sensitivities can be increased by filling of deep electron/hole traps in the energy ranges between 75 and 105 kVp, and they exhibited no significant variations according to the bleaching time.

Characterization of Tissue Equivalent Materials Using 3D Printing for Patient-Specific DQA in Radiation Therapy

Three-dimensional printing technology has the advantage of facilitating the construction of complex three-dimensional shapes. For this reason, it is widely used in medical and radiological fields. However, few materials with high electron density similar to that of bone exist for fabricating a human phantom. In this study, commercially available filament materials were used with an FDM 3D printer to perform delivery quality assurance (DQA) and were evaluated for medical use. For the bone filament material, BaSO4 was synthesized in five ratios of 2%, 4%, 6%, 8%, and 10% with 40% PBAT and 50~58% PLA. The electron density for the 3D printing material fabricated was obtained using kV energy CT and compared with the electron density of human organs and bones. The radiation beam properties of the 3D printed structures were analyzed as films for treatment using a linear accelerator. As a result, by changing the infill density of the material, it was possible to produce a material similar to the density of human organs, and a homogeneous bone material with HU values ranging from 371 ± 9 to 1013 ± 28 was produced. The 3D printing material developed in this study is expected to be usefully applied to the development of a patient-specific phantom to evaluate the accuracy of radiotherapy.

Al2O3:C and LiF: Mg, Ti characterisations at 100–150 kV energy range for computed tomography dose measurement

Performance characterisation has been carried out of nanoDot™ OSLDs and TLD-100™, validating their use for diagnostic x-ray dose profile assessments. Investigations include optical annealing, signal depletion, signal fading, dose-response, sensitivity, and energy dependence. Both dosimeter types were exposed using the Constant Potential Industrial X-ray (Model Philips MG 165) in Standard Radiation Qualities (RQT) procedure located in Nuclear Malaysia, Bangi. OSLD annealing using a 14 W compact fluorescent lamp showed an average signal loss of ∼93% as a result of 60 min of illumination. For dosimetric signal depletion, screened nanoDot™ OSLDs gave rise to the most favorable performance, with a mean signal loss of 1.0% per reading. In respect of signal fading, similar favorable performance was found for the screened nanoDot™ OSLDs, after a stabilisation period of 11–12 days post-irradiation, the average reading decreased by ∼1% over a further 17 days. For doses up to 500 mGy the TLD-100™ and screened nanoDot™ OSLDs both provide a highly linear response, with a regression coefficient of 0.999 in both cases. Linear energy dependence was found for RQT spectra from 100 to 150 kV.

Non-thermal plasma removal of naphthalene as tar model compound from biomass gasification

Gasification of biomass is an industrial process utilized to produce product gas that can be used in electrical power generation with internal combustion engines. However, there remain huge challenges with regards to tar and other pollutants, thus their removal before further use is necessary. Non-thermal plasma method can be considered as a novel and efficient way for treatment of tar from product gas. In this work, a laboratory-scale, reverse vortex flow gliding arc plasma reactor was developed and tested for the removal of tar model compound using naphthalene as surrogate. Effects of total gas feed rate in the range of 20–60 L/min, applied voltage in the range of 50–220 V, hence, power input in the range of 300–460 W with initial naphthalene concentration of 610 ± 50 mg/m3 on removal and energy input were investigated. It was found the tar removal efficiency increased with increasing applied voltage. Maximum naphthalene removal efficiency of 85% was achieved at applied high voltage of 15 kV and specific energy input of 0.13 kWh/m3 with energy utilization efficiency of about 4.60 g/kWh. From the findings, non-thermal plasma technology appeared to offer great potential in the removal of biomass tar from gasification. The technology may be promising for possible application to real biomass tar cracking and upgrading of product gas from gasification.

Using micro silica bead TLDs in high dose rate brachytherapy dosimetry: A phantom study

In vivo dosimetry (IVD) is a powerful method for treatment dose verification which has been applied in brachytherapy (BT) using different dosimetry systems and technologies. However, implementation of IVD in routine clinical workflow and patient quality control is limited in many departments. This is due to challenges related to the high gradient dose distribution, large dose range and dose rate around BT sources. The apparent lack of utilization of high accuracy IVD systems, which are straightforward to use in a clinic, is currently a significant missed opportunity for quality and safety assurance. Commercial silica bead thermoluminescent dosimeters (TLDs) (Jafari et al., 2014a, 2014b) appear suitable for IVD in high dose rate (HDR) BT. The dose response of silica bead TLDs was characterized in a water phantom and a constructed anthropomorphic pelvis phantom by exposing them with 60Co source as the used source in our BT department. Also dose response of bead TLDs was defined in a CTDI phantom with 120 kV energy exposure. It was found that measured dose differences to planning system calculations varied from −2.0% to 2.9% during pelvis phantom investigations. Mean experimental dose differences did not exceed the standard uncertainty 7.0% (k = 2) estimated for this study. The phantom results presented indicate that silica beads TLDs may be used to provide in vivo verification of delivered dose in intracavitary HDR BT although this work verifies use only for 60Co source.

Image contrast assessment of metal-based nanoparticles as applications for image-guided radiation therapy.

Metal-based nanoparticles (NPs) have been extensively studied for dose enhancement applications in radiation therapy. This study investigated the utility of such NPs for image-guided radiation therapy (IGRT). Phantom images of gold NPs (AuNPs) and titanium peroxide NPs (TiOxNPs) with different concentrations were acquired using IGRT modalities, including cone-beam computed tomography (CBCT). AuNPs induced strong contrast enhancement in kV energy CBCT images, whereas TiOxNPs at high concentrations showed weak but detectable changes. The results indicated that these NPs can be used to enhance IGRT images as well as dose enhancement for treatment purposes.

Power on! Low-energy electrophysical treatment is an effective new weed control approach.

Environmental concerns are driving the call for adoption of alternative nonchemical weeding approaches. This study aimed to develop and evaluate a novel, precise, low-energy electrophysical treatment weeding systems and to provide new insight into their control mechanism. Two electrophysical treatment systems, based on AC (2.2 kV) and DC (40 kV) energy sources, were developed and evaluated. The impacts of various operational and biological factors on the weed control effectiveness were evaluated. Additionally, thermal images were taken during the treatments to document plant temperature. Treatments via direct leaf contact caused greater damage to Amaranth plants than the stem contact treatments, with 75% and 20% biomass reduction compared to control, respectively. Treatment of early growth stages was favorable over later growth stages, with 100% and 75% biomass reduction for Trifolium pretense plants treated with 0.0125 W h 2 and 4 weeks after seeding, respectively, compared to control. Additionally, the applied energy affected treatment performance, with its impact varying across the growth stages and species; at the two-leaf growth stage, 0.0025 W h treatment was sufficient for plant death. A >40 °C increase in plant temperature was measured during the electrophysical treatment, with the temperature of some plant organs reaching ~70 °C. Results from this study demonstrate the potential use of electrophysical treatment as an effective weed control tool. The low energetic demands in the new systems provide suitable control results when applied at early stages. Temperature increase seemed to be one of the main control factors, yet efficacy was affected by various biological factors.

Integrating X-ray kV millimetric field dosimetry with a synthetic diamond detector into the treatment planning system commissioning of a preclinical irradiator.

Small animal irradiators are equipped with x-ray beams and cone collimators with millimeter dimensions to be used in preclinical research. The use of small fields in the kV energy range may require the application of energy-dependent, field size-dependent, or depth-dependent correction factors to the dosimetric data acquired for treatment planning system (TPS) commissioning purposes to obtain accurate dose values. Considering that these corrections are also detector dependent, the suitability of a synthetic single-crystal diamond detector for small-field relative dosimetry in a preclinical irradiator (220-kVp) was evaluated to avoid the necessity of applying correction factors during TPS commissioning. The detector response was assessed during the transition for field sizes ranging from 20×20mm2 to 3×3mm2 , using the small animal radiation research platform (SARRP). The percentage depth dose distributions (PDDs), lateral profiles and output factors (OFs) were measured. The PDDs for the synthetic diamond detector were compared to the distributions acquired using a small-volume microchamber (0.016cm3 ) and with Monte Carlo calculations using the MC3D in-house software package. The profiles and OFs were compared to the data from a silicon solid-state detector and to radiochromic film data provided by the manufacturer; for the OF determination, measurements made using a microchamber were added for comparison. The performance of several detectors used as references was previously validated for relative dosimetry in preclinical irradiators. A commercial TPS was commissioned for the factor-based algorithm, using the data acquired with the diamond detector, and no additional correction factors were applied. To verify the performance of the TPS and the accuracy of the dosimetric methodology, radiochromic film irradiation in water was conducted, and two-dimensional (2D) dose distributions in the coronal and axial planes were compared under different gamma criteria. Compared with the microchamber and MC3D distributions, the agreement of the PDDs using the synthetic diamond detector was better than 2%. The profile data exhibited very good agreement compared with the data from the silicon detector, with an average and a maximum difference of 0.31 and 0.39mm in the penumbras, respectively. Compared with the data from the radiochromic film, the average and maximum differences were equal to 0.77 and 0.89mm, respectively. Very good agreement, within 1%, was obtained between the OFs measured with the synthetic diamond detector and the radiochromic film, compared only for the cone collimators. The validation of the TPS commissioning using gamma criteria compared to film showed an average passing rate of 100% and 93.2% with a global gamma criterion of 1mm/3% for the coronal and axial planes, respectively, including the 3×3mm2 field size and penumbra regions. Synthetic diamond is a suitable detector for the complete relative dosimetry of small x-ray fields. The commissioning of the TPS with its own beam dosimetric data exhibited encouraging results even in a 3×3mm2 field and penumbra region. This methodology allows for the prediction of 2D dose distributions with an accuracy in water ranging from 3 to 5% compared to the 2D distribution from film dosimetry.

P53.05 Evaluation of IGRT-Induced Imaging Doses and Secondary Cancer risk for SBRT Early Lung Cancer Patients in Silico Study

The imaging dose produced by Image guided radiotherapy (IGRT) will increase the secondary cancer risk.This study performed dosimetry studies and secondary cancer risk assessments on using electronic portal imaging device (EPID) and cone beam computed tomography (CBCT) as image guided tools for the early lung cancer patients treated with SBRT. This study retrospectively analyzed the treatment plans of sixty-one early lung cancer patients treated with SBRT. The imaging doses from MV-EPID and kV-CBCT of the Edge accelerator were added to treatment plans. The MV-EPID imaging dose (6MV Photon beam) was calculated in Pinnacle TPS, and the kV-CBCT imaging dose was simulated and calculated by modeling of the kV energy beam in TPS using Pinnacle automatic modeling program. Three types of plans, namely PlanEPID, PlanCBCT and Planorigin, were generated with incorporating doses of EPID, CBCT and no imaging, respectively, for analysis. The effects of imaging doses on dose-volume-histogram (DVH) criteria and plan quality were analyzed, and the excess absolute risk (EAR) of secondary cancer for ipsilateral lung was evaluated. The regions that received less than 50cGy were significantly impacted by the imaging doses, while the isodose lines greater than 1000cGy were barely changed. The DVH values of ipsilateral lung increased the most in PlanEPID, followed by PlanCBCT. Compared to Planorigin on the average, the estimated EAR of ipsilateral lung in PlanEPID increased by 3.43%, while the corresponding EAR increase in PlanCBCT was much smaller (about 0.4%). Considering only the contribution of the imaging dose, the EAR values for the ipsilateral lung due to the MV-EPID dose in 5 years,10 years and 15 years were 1.49 cases, 2.09 cases and 2.88 cases per 104PY respectively, and those due to the kV-CBCT dose were about 9 times lower, correspondingly. The imaging doses produced by MV-EPID and kV-CBCT had little effects on the target dose coverage. The secondary cancer risk caused by MV-EPID dose is more than 8.5 times that of kV-CBCT.

Evaluation of IGRT-Induced Imaging Doses and Secondary Cancer Risk for SBRT Early Lung Cancer Patients In Silico Study.

Objectives:This study performed dosimetry studies and secondary cancer risk assessments on using electronic portal imaging device (EPID) and cone beam computed tomography (CBCT) as image guided tools for the early lung cancer patients treated with SBRT.Methods:The imaging doses from MV-EPID and kV-CBCT of the Edge accelerator were retrospectively added to sixty-one SBRT treatment plans of early lung cancer patients. The MV-EPID imaging dose (6MV Photon beam) was calculated in Pinnacle TPS, and the kV-CBCT imaging dose was simulated and calculated by modeling of the kV energy beam in TPS using Pinnacle automatic modeling program. Three types of plans, namely PlanEPID, PlanCBCT and Planorigin, were generated with incorporating doses of EPID, CBCT and no imaging, respectively, for analysis. The effects of imaging doses on dose-volume-histogram (DVH) and plan quality were analyzed, and the excess absolute risk (EAR) of secondary cancer for ipsilateral lung was evaluated.Results:The regions that received less than 50 cGy were significantly impacted by the imaging doses, while the isodose lines greater than 1000 cGy were barely changed. The DVH values of ipsilateral lung increased the most in PlanEPID, followed by PlanCBCT. Compared to Planorigin on the average, the estimated EAR of ipsilateral lung in PlanEPID increased by 3.43%, while the corresponding EAR increase in PlanCBCT was much smaller (about 0.4%). Considering only the contribution of the imaging dose, the EAR values for the ipsilateral lung due to the MV-EPID dose in 5 years,10 years and 15 years were 1.49 cases, 2.09 cases and 2.88 cases per 104PY respectively, and those due to the kV-CBCT dose were about 9 times lower, correspondingly.Conclusions:The imaging doses produced by MV-EPID and kV-CBCT had little effects on the target dose coverage. The secondary cancer risk caused by MV-EPID dose is more than 8.5 times that of kV-CBCT.

Technical Note: Vendor miscalibration of preclinical orthovoltage irradiator identified through independent output check.

Accurate radiation dosimetry in radiobiological experiments is crucial for preclinical research in advancement of cancer treatment. Vendors of cell irradiators often perform calibration for end-users. However, calibration accuracy remains unclear due to missing detailed information on calibration equipment and procedures. In this study, we report our findings of a vender miscalibration of the radiation output and our investigation on the root cause of the discrepancy. Independent calibration verification for a commercial preclinical orthovoltage irradiator was conducted. Initially, in the absence of ionization chambers calibrated at kV energy, radiochromic films (EBT3) was first calibrated at MV energy. Energy correction factors from literature were used to create an in-house kV dosimetry system. The miscalibration identified with the in-house kV EBT3 dosimetry was later confirmed by ADCL calibrated ionization chambers (Exradin A1SL and PTW 30013) at kV energy. Ionization chambers were suspended in-air following TG-61 recommendation for output calibration. To investigate the root cause of the miscalibration, additional measurements were performed with ionization chambers placed on the shelf. A validated Monte Carlo simulation code was also used to investigate the impact of placing the ionization chamber on the shelf instead of suspending it in air during the vendor-performed calibration process. Up to a 6% dosimetry error was observed when comparing the vendor calibrated output of the preclinical irradiator with our independent calibration check. Further investigation showed incorrect setups in the vendor's calibration procedure which may result in dose errors up to 11% from the backscatter of the shelf board during calibration, and up to 5% from omitting temperature and pressure corrections to ionization chamber readings. Our study revealed large dose calibration errors caused by incorrect setup and the omission of temperature/pressure correction in the vendor's calibration procedure. The findings also highlighted the importance of performing an independent check of the dose calibration for preclinical kV irradiators. More absolute dosimetry training is needed for both vendors and end users for establishing accurate absolute dosimetry.